Robots can be navigated in a variety of ways during transportation, loading, unloading, and other tasks. For example, the robots can be navigated through a global positioning system (GPS), or can also be navigated through fiducial markers. When the robots are used for parcel sorting, a sorting system has hundreds of robots moving at the same time. At present, the most common method is to perform navigation by collecting fiducial marker information. The most common fiducial marker format is a two-dimensional code. The two-dimensional code includes both direction indication and position indication. When the robot moves from one module area to another module area, the robot reads two-dimensional code information, and responds by going straight, going backward, turning and the like according to instructions. Such two-dimensional codes have a good error tolerance rate; decoding of the position information can even be performed in the absence of some information. Information at four corners of the two-dimensional code represents direction information, and the direction information can be used to enable the robot to determine its direction. However, when any piece of information at the four corners of the two-dimensional code fails to be read, the direction cannot be determined. A failure to read the information at the four corners will arise when abrasion, blockage by foreign matter, and the like, occur on the two-dimensional code.